Different EGF receptors are known, such as EGFR1, HER-2/neu, HER-3, HER-4.
Particularly HER-2/neu has been proposed as target for antitumor strategies (WO 90/14357).
The proto-oncogene HER-2/neu codes for a 185 KDa membrane receptor protein (p185) (Schechter, A. et al. 1984, Nature 312/513).
The functions of HER-2/neu are presently not well known but they seem to be associated to the increase of tyrosine kinase activity (Di Fiore, P. et al. 1990 Mol. Cell. Biol. 10:2749).
Different ligands, which can induce both stimulatory and inhibitory signals depending on the ligand and/or the experimental conditions, were proposed for the receptor (Peles, E. et al. 1992 Cell. 69:205).
HER-2/neu is expressed during placentation and organogenesis (Kokay. Y et al. 1987 Proc. Natl. Acad. Sci. U.S.A. 84:8498; Knezevic V. et al. 1994 J. Anat. 1985:181) and it is detectable in small amounts in a number of epithelial/glandular adult tissues (Press. M. et al. 1990 Oncogenes. 5:953).
Mutations and/or overexpression of p185 are associated to tumor pathogenesis. The proto-oncogene is activated by punctiform mutations (Bargmann, C. & Weimberg R. A. 1988 EMBO J. 7:2043). In man mutations were not found and it was found that in the carcinomas of glandular origin (e.g. breast, ovary, lung and kidney adenocarcinomas), the transforming activity is related to an amplification/overexpression of p185 with normal structure.
The amplification of p185 has been associated with an unfavourable prognosis in patients with breast carcinoma (Yokota, J. et al. 1986 Lancet. i. 765; Slamon. D. J. et al. 1987 Science. 235:1772; Yonemura. Y. et al. 1991. Cancer Research. 51:1034, Gustarson. B. A. et al. 1992. Europ. J. Cancer. 28:263).
Recent studies also suggest a connection between the receptor overexpression and the phenomenon of drug resistance.
In fact, carcinomas overexpressing HER-2/neu are insensitive to 5-fluoruracyl treatment (Paikj S. M. et al. 1991 Proc. Am. Assoc. Cancer Resear. 32, 291). This was confirmed by transfection studies of HER-2/neu in breast carcinoma cell lines becoming resistant to Tamoxifen and cisplatin (Benz C. C. et al. 1992 Breast Cancer Research Treat. 24, 84).
The patients at stage I of breast carcinoma, with good prognosis but with immunochemically detectable HER-2/neu, relapse after chemiotherapeutic treatment (Alfred D. C. et al. 1992 J. Clin. Onc. 10, 599 and Gusterson B. A. et al. 1992 J. Clin. Onc. 10, 1049). Moreover, anti-HER-2/neu antibodies increase the cisplatin and tumor necrosis factor (TNF) cytotoxicity against the breast and ovary carcinoma (Hancock M. C. et al. 1991 Canc. Res. 51, 4575 and Hudziac R. M. 1989 Mol. Cell. Biol. 9, 1165). On the other hand, in the drug resistant cell lines, the amount of epidermal growth factor (EGF) receptor is increased (Meyers M. B. et al. 1986 Proc. Natl. Acad. Sci. U.S.A. 83, 5521), and the antibodies against said receptors increase the cytotoxic effects of drugs (Aboud-Pirak E. et al. 1988 J. Natl. Canc. Inst. 80, 1605; Baselga J. et al. 1993 J. Natl. Canc. Inst. 85, 1327).
Similarly to antibodies also EGF increases the cytotoxic effect of alkylating agents such as cisplatin, of ionizing rays, of mytomicin, of 5-fluoruracyl and of adriamycin (Christen R. D. 1990 J. Clin. Inv. 86, 1632; Kowk T. T. et al. 1989 J. Natl. Canc. Inst. 81, 1020; Amagase H. et al. 1990 J. Pharm. Dyn. 13, 263; Amagase H. et al. XXX Jpn. J. Canc. Res. 80, 670; Kowk T. T. et al. 1991 Int. J. Cancer 49, 73).
The small amounts of p185 expressed in normal epithelia in comparison to the larger amounts in cancer tissues induced to believe that the receptor may act as target antigen for passive immunotherapeutic strategies, (e.g. by administering monoclonal antibodies). It is known, for instance, that some anti-p185 monoclonal antibodies can inhibit the growth of breast carcinoma cells both in vitro and in nude mice (Marx. J. 1993 Science 259:226).
Recently it has been demonstrated that anti-erbB-2 monoclonal antibodies can exert a cytostatic effect on tumor by down-regulation of the receptor itself (Katsumatu M. et al., 1985, Nature Medicine 1:644-648).
Although active immunization strategies (vaccination) were proposed for this antigen, this hypothesis was prejudiced by the possibility that the induced immunity could be toxic for the epithelia physiologically expressing this antigen.
On the other hand, the inoculation of recombinant vaccinia viruses expressing the extracellular domain of neu oncogene completely and specifically protected mice against tumor cells expressing this antigen (Bernards. R. et al. 1987 Proc. Natl. Acad. Sci. U.S.A. 84:6854).
Since the growth factors and their receptors play a central role as autocrine and paracrine regulatory circuits not only during tumorigenesis but also during embryonic development, experimental models based on both these developmental processes are particularly significant for the purposes of this invention.